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Global variables in Registers (MSP430)

Ryan Joy
Prodigy 30 points

I have a mixed C/ASM project and I'm wondering if it is possible to reserve one or two registers for global variables. With IAR you can tell the compiler not to use R4 and/or R5 so I'm wondering if there is a way to accomplish the same thing in CCS 4.2.

Thanks

-Ryan

  • 0
    TI__Guru**** 253230 points

    I'm not sure which MSP430 compiler version comes with CCS 4.2.  I think it is v3.3.0.  If so, you can use the new option --global_register.  It is not documented in the compiler manual yet.  But you can run cl430 from the command line and get summary information like this.

    % cl430 -h --global_register
  --global_register=r5,r4
                          Reserve the specified register for use by the user.
                           It will not be used by the compiler.  If only
                           reserving one global register it is preferable for
                           performance reasons to reserve r4.

    Hope this helps,

    -George

  • 0 in reply to George Mock
    Prodigy 30 points

    Thanks, George. That is exactly what I was hoping for. BTW, CCS 4.2 includes version 3.3.1 of the compiler.

    -Ryan